by Girish Gupta, Special for USA TODAY

by Girish Gupta, Special for USA TODAY

CARACAS, Venezuela - President Hugo Chávez has received more chemotherapy since a December operation in Cuba, the country's vice president revealed late Friday night.

Vice President Nicolás Maduro said Chávez "continues his battle for life." The ailing 58-year-old has not been seen or heard from since he returned to the country on Feb. 18.

The vice president quoted Chávez as saying he decided to return to Venezuela because he was entering "a new phase" of "more intense and tough" treatments and wanted to be in Caracas for them.

Maduro's disclosure came after members of the government held a Mass on Friday at a new chapel built inside the military hospital in Caracas where Chávez is reportedly staying.

At the Mass, hymns were sung while images flashed across television screens of an angelic, glowing Chávez in his younger days. The Mass was broadcast live on state television.

Maduro's offering of the most detailed rundown to date of Chávez's post-operative struggle came hours after an accusation by opposition leader Henrique Capriles that the government has repeatedly lied about Chávez's condition.

"We'll see how they explain to the country in the (coming) days all the lies they've been telling about the president's situation," Capriles, whom Chávez defeated in Oct. 7 elections, said in a tweet.

Chávez has not been seen or heard from since going to Cuba for his fourth cancer surgery, except for a set of "proof of life" photos released Feb. 15 while he was still in Havana.

Little information has been revealed about Chávez's cancer. The type of cancer is not known. Four operations have taken place since the cancer was announced in June 2011.

Maduro, 50, angrily countered demands for information on Chávez's health. "Sadly, the opposition live in a world of hatred, wrongdoing, bad feelings and bad desires," he said.

"Stop the attacks on the commander! Stop the rumors, stop trying to create instability!" Maduro added.

Chávez still remains popular with many in the country. At a government rally Wednesday, Manuel Castillo Trejo, 47, said, "My comandante will be back ... He just needs to rest."

But the lack of transparency on his condition has jilted some. "It's unbelievable that this is happening in this day and age," said Carlos Rivero, a 42-year-old engineer based in Caracas, referring to the lack of information on Chávez 's health.

Should Chávez be unable to continue to govern, new elections could be called within 30 days, likely pitting Maduro against Capriles.

Campaigning appears to have begun, with insults traded between the government and Capriles. "A presidential election has not yet been called but we have to be prepared," Capriles said. "We are ready."

While passion for Chávez far outstrips that for Maduro among government supporters, Capriles is likely to lose any forthcoming election, according to polls. Maduro would surf the momentum offered by Chávez 's death.

"The death of a leader at the height of his popularity would be very powerful for elections," said Caracas pollster Luis Vicente León. "The funeral for Chávez would merge into the election campaign."

Meanwhile, the opposition has demanded answers from the government. "We believe in facts not rumors," said Roderick Navarro, a 25-year-old organizer of student protests on the government's lack of information. "The government needs to show us whether Chávez can govern or not."